1. Field of the Invention
The present invention relates to a fusing device of an electrophotographic image forming apparatus, and, more particularly, to a structure of end portions of a fusing roller.
2. Description of the Related Art
Generally, in an electrophotographic color image forming apparatus such as a color laser printer, a predetermined electrostatic latent image is formed on a photosensitive body, and the electrostatic latent image is developed with a toner, and the developed resultant is transferred onto a sheet of paper after passing through a predetermined transfer medium. In addition, the resultant that is transferred on the sheet of paper is heated and pressed to be permanently fused thereon.
Referring to FIG. 1, the conventional electrophotographic color image forming apparatus includes a photosensitive drum 10, a charger 11 that charges the photosensitive drum 10, a laser scanning unit 12 that is a light scanning unit to form a predetermined electrostatic latent image on the charged photosensitive drum 10 by scanning the light, a developing unit 13 that develops the electrostatic latent image with toners of four colors, that is, yellow (Y), magenta (M), cyan (C), and black (K) colors, a transfer belt 14 that sequentially overlaps the images of four colors formed on the photosensitive drum 10, a first transfer roller 14a that transfers the four color images that is developed on the photosensitive drum 10 onto the transfer belt 14, a second transfer roller 14b that transfers the four color images on the transfer belt 14 onto the sheet of paper, and a fusing device 15 that heats and presses the sheet of paper to permanently fuse the transferred image on the sheet of paper.
Reference numeral 16 denotes a paper cassette, reference numeral 17 denotes a blade to clean the photosensitive drum, reference numeral 18 denotes an eraser, and reference numeral 19 denotes a conveying path through which the sheet of paper may be discharged.
The fusing device 15 heats the sheet of paper, on which the toner images are transferred to melt the toner image in a powder state and to fuse the image on the sheet of paper. The fusing device 15 includes a fusing roller that fuses the toner on the sheet of paper, and a pressing roller that pushes the sheet of paper toward the fusing roller.
The fusing roller is formed as a cylindrical roller made of metal, such as stainless steel, that has a rubber member formed on a circumference thereof. The metal cylindrical roller allows a temperature of the fusing roller to be substantially uniform, and the rubber member softly contacts the sheet of paper that passes between the pressing roller and the fusing roller.
The fusing roller is a rotating body and has a structure that allows an electrical connection to a heating element to be included therein.
U.S. Pat. No. 6,628,917 discloses a fusing roller, both sides of which are attached by end caps. The end cap is a resin such as polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), or a nylon that is filled with a filler, such as glass fiber, having a low thermal conductivity at a high temperature.
When a surface temperature of the fusing roller is high, the temperature of the cylindrical roller is higher than the surface temperature of the fusing roller, and the end cap may melt.
On the other hand, Japanese Laid-open Patent No. H10-3223 discloses a fusing roller that has bearings installed on both end portions thereof, and a gear is installed on one end portion of the fusing roller. Here, an adiabatic member is used between the fusing roller and the bearing.